The use of radiofrequency identification (RFID) devices such as RFID tags, electronic shelf labels (ESLs) and other RFID devices that provide information and receive information and commands wirelessly through means such as reflective backscatter is becoming more and more common. Such devices are deployed in many different facilities, with each facility having its own individual characteristics affecting the signals that are transmitted to and returned from the devices.
Many facilities using RFID devices employ large numbers of RFID devices with multiple RFID communication and control devices, such as communication base stations and RFID readers. Such RFID communication and control devices will be referred to here generally as “RFID communication devices,” or simply “communication devices,” for convenience, but it will be recognized that communication devices referred to here may, depending on the design and use of the specific device, simply read information from an RFID device or may send information and commands to and receive information from a device. RFID communication devices may be deployed in numerous different locations in a facility, and one or more communication devices may be portable communication devices that are moved about a facility. The effectiveness with which a communication device performs communication depends in significant part on the conditions prevailing at the specific location in which the particular communication device is placed. Such conditions include the presence, absence, type, and degree of electromagnetic interference and noise, as well as the presence and nature of obstructions that may shield a communication device from signals intended to be used for communication. Noise or interference affecting a communication device may include passive noise or passive interference, such as reflections or returns of signals emitted by the communication device. A communication device may also be affected by active noise or interference, which includes signals emitted by active sources operating independently of any signals emitted by the communication device. Each location in a facility at which a fixed communication device is placed can be expected to be subject to a set of conditions that may be unique in combination. In addition, portable or mobile communication devices may pass through numerous locations having differing characteristics.
It is difficult to understand and correct or compensate for the conditions affecting a particular communication device without an understanding of the specific conditions affecting that communication device. Surveying the general environment is frequently costly and time consuming, and typically does not accurately show the specific conditions at each communication device.
It is possible to take steps to reduce interference and signal blockage, or to mitigate their effects, but it is difficult to do so when the environments in which such devices are used may change rapidly. For example, in grocery stores or warehouses, products are constantly being moved, and at different times, particular shelves may be full, partially full, or empty of products, or may have changing mixes of products stocked thereon. Differing contents of shelves may have significantly differing effects on communication.